linux-kernel - Re: [PATCH 7/9] net: centralize ns

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <yfd2esldmb63p3cv43gbnqy4xsefqfdlbfpoi2sr3crocmptp5@ouvz5orl7zlo>
Date: Mon, 22 Sep 2025 12:19:43 +0200
From: Jan Kara <jack@...e.cz>
To: Christian Brauner <brauner@...nel.org>
Cc: Jan Kara <jack@...e.cz>, linux-fsdevel@...r.kernel.org, 
	Amir Goldstein <amir73il@...il.com>, Josef Bacik <josef@...icpanda.com>, 
	Jeff Layton <jlayton@...nel.org>, Mike Yuan <me@...dnzj.com>, 
	Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, Lennart Poettering <mzxreary@...inter.de>, 
	Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Michal Koutný <mkoutny@...e.com>, Jakub Kicinski <kuba@...nel.org>, 
	Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH 7/9] net: centralize ns_common initialization

On Fri 19-09-25 10:08:33, Christian Brauner wrote:
> On Thu, Sep 18, 2025 at 11:42:38AM +0200, Jan Kara wrote:
> > On Wed 17-09-25 12:28:06, Christian Brauner wrote:
> > > Centralize ns_common initialization.
> > > 
> > > Signed-off-by: Christian Brauner <brauner@...nel.org>
> > > ---
> > >  net/core/net_namespace.c | 23 +++--------------------
> > >  1 file changed, 3 insertions(+), 20 deletions(-)
> > > 
> > > diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> > > index a57b3cda8dbc..897f4927df9e 100644
> > > --- a/net/core/net_namespace.c
> > > +++ b/net/core/net_namespace.c
> > > @@ -409,7 +409,7 @@ static __net_init int preinit_net(struct net *net, struct user_namespace *user_n
> > >  	ns_ops = NULL;
> > >  #endif
> > >  
> > > -	ret = ns_common_init(&net->ns, ns_ops, false);
> > > +	ret = ns_common_init(&net->ns, ns_ops, true);
> > >  	if (ret)
> > >  		return ret;
> > >  
> > > @@ -597,6 +597,7 @@ struct net *copy_net_ns(unsigned long flags,
> > >  		net_passive_dec(net);
> > >  dec_ucounts:
> > >  		dec_net_namespaces(ucounts);
> > > +		ns_free_inum(&net->ns);
> > 
> > This looks like a wrong place to put it? dec_ucounts also gets called when we
> > failed to create 'net' and thus net == NULL. 
> > 
> > >  		return ERR_PTR(rv);
> > >  	}
> > >  	return net;
> > > @@ -718,6 +719,7 @@ static void cleanup_net(struct work_struct *work)
> > >  #endif
> > >  		put_user_ns(net->user_ns);
> > >  		net_passive_dec(net);
> > > +		ns_free_inum(&net->ns);
> > 
> > The calling of ns_free_inum() after we've dropped our reference
> > (net_passive_dec()) looks suspicious. Given how 'net' freeing works I don't
> > think this can lead to actual UAF issues but it is in my opinion a bad
> > coding pattern and for no good reason AFAICT.
> 
> All good points. I can't say I'm fond of the complexity in this specific
> instance in general.

Agreed. The changes look good to me now. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> 
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 897f4927df9e..9df236811454 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -590,6 +590,7 @@ struct net *copy_net_ns(unsigned long flags,
> 
>         if (rv < 0) {
>  put_userns:
> +               ns_free_inum(&net->ns);
>  #ifdef CONFIG_KEYS
>                 key_remove_domain(net->key_domain);
>  #endif
> @@ -597,7 +598,6 @@ struct net *copy_net_ns(unsigned long flags,
>                 net_passive_dec(net);
>  dec_ucounts:
>                 dec_net_namespaces(ucounts);
> -               ns_free_inum(&net->ns);
>                 return ERR_PTR(rv);
>         }
>         return net;
> @@ -713,13 +713,13 @@ static void cleanup_net(struct work_struct *work)
>         /* Finally it is safe to free my network namespace structure */
>         list_for_each_entry_safe(net, tmp, &net_exit_list, exit_list) {
>                 list_del_init(&net->exit_list);
> +               ns_free_inum(&net->ns);
>                 dec_net_namespaces(net->ucounts);
>  #ifdef CONFIG_KEYS
>                 key_remove_domain(net->key_domain);
>  #endif
>                 put_user_ns(net->user_ns);
>                 net_passive_dec(net);
> -               ns_free_inum(&net->ns);
>         }
>         WRITE_ONCE(cleanup_net_task, NULL);
>  }
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR